Spread arguments length check doesn't work with function overloads

[bowenni]

TypeScript Version: 2.9.0-dev.20180422

Search Terms: spread, overload

Code

function foo(): void;
function foo(...args: {}[]): void {}

function bar(...args: {}[]) {
  foo(...args);
}

Expected behavior:
No Errors.

Actual behavior:
error TS2556: Expected 0 arguments, but got 1 or more.
If I just swap the order of the declarations of function foo it works.

Playground Link:
https://www.typescriptlang.org/play/#src=function%20foo()%3A%20void%3B%0D%0Afunction%20foo(...args%3A%20%7B%7D%5B%5D)%3A%20void%20%7B%7D%0D%0Afunction%20bar(...args%3A%20%7B%7D%5B%5D)%20%7B%0D%0A%20%20foo(...args)%3B%0D%0A%7D

Related Issues:
#20071 is the fix for excess spread operator check.
#21906 is very close to my issue, but not quite the same.

[mhegazy]

The implementation signature is not considered part of the overloads for the method. in other words, foo has one overload that takes no arguments.

if you want to call the function with with variable number of arguments add a new overload:

function foo(): void;
function foo(...args: {}[]);
function foo(...args: {}[]): void {}

[bowenni]

Thanks for the quick reply! Adding a new overload solved the problem for me.

Would you consider The implementation signature is not considered part of the overloads for the method intended or bug? It feels counter intuitive that I have to explicitly declare a new overload even though I have an implementation already.

[AlCalzone]

Having the exposed overloads separate from the implementation allows to expose nice and cleanly typed overloads while having an ugly internal implementation signature that just exists to match all the “official” function signatures.
So definitely a feature IMO

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.